A standard drive chain comprises a plurality of pairs of link elements with the elements of each pair extending longitudinally parallel to each other and having relatively widely spaced outer ends formed with bores and relatively closely spaced inner ends formed with axially throughgoing and transversely aligned bores, Each pair of inner ends lies between a respective pair of outer ends with the bores coaxial and receives a respective pin having ends seated in the bores of the respective outer ends. Respective sleeves surround the pins between the respective inner ends. Such a chain is looped over sprockets so the one sprocket can drive the other.
Normally as described in U.S. Pat. No. 5,069,509 of Johnson, the pin ends are fixed in the outer link-element ends. The inner link-element ends are engaged over the ends of an inner sleeve which itself rotates on the pin and an outer sleeve is provided on the inner sleeve to hold the inner link-element ends apart. This is a fairly complex structure that is expensive to manufacture.
In U.S. Pat. No. 5,183,318 of Taft only one sleeve is used which can rotate freely on the pin. An extra ring is journaled on the pin to carry the inner link-element ends. While this system has reduced friction, it is once again complex to manufacture because of all the seals needed and these seals are subjected to particularly great lateral stresses. If a single seal fails, the respective link can be expected to wear out rapidly.
The systems described in commonly owned German patent 4,410,388 filed Mar. 25, 1994 and U.S. patent application Ser. No. 08/838,326 (now U.S. Pat. No. 5,829,580) use specific wear-resistant materials and shapes to reduce wear and simplify the problems of sealing the various regions needing lubrication. These systems represent an advance, but still could use improvement.